This invention relates generally to an apparatus for severing and feeding a thermoplastic sheet to a forming machine, and, more particularly, to apparatus for severing a sheet continuously produced from an extruder and successively feeding a desired length of the severed plastic web to an intermittently operated forming machine.
Various thin walled articles of thermoplastic material such as cups, trays, buckets, tubes and the like have been produced by means of forming machines comprising a pair of male and female dies adapted to move between the closed position and the open position where heated and consequently softened thermoplastic sheet is brought between the separated dies by means of a pair of endless link chains respectively provided with a plurality of clamps so as to grasp opposite side edges of the sheet.
It is possible of course to heat the plastic webs each previously prepared in a desired length up to a temperature suitable for thermal forming method ranging from 130.degree. to 180.degree. C. which is varied depending on the type of material and to then feed each to the forming machine.
It is obviously preferable, however, to combine the forming machine with the extruder in a line so that the plastic sheet extruded from the fish tail-shaped nozzle thereof and at a fairly high temperature, for instance, ranging from 200.degree. to 240.degree. C. is directly fed to the forming machine.
In this direct feeding method, some means must be provided so as to compensate for the lag caused from the continuous extrusion of the sheet and the intermittent feeding of the continuous sheet or severed webs to the forming machine. This compensation has generally been made by the so-called dancing roll means, but it is not always satisfactory above all when operating at a high speed as is well known to those skilled in the art.